1. Field of the Invention
The invention relates to a moisture control system for an exhaust pipe for an internal combustion engine and, more particularly, relates to a vertically-extending exhaust pipe that includes a drain for the removal of rainwater and other fluids which, in the absence of a rain guard, would otherwise be directed to upstream exhaust system components or the engine.
2. Discussion of the Related Art
Many industrial and agricultural machines that are powered by an internal combustion engine have an exhaust system that terminates in a vertically-extending exhaust pipe exhausting gases from the engine to a position above the machine. These machines include farm tractors, some semi-tractors, and a variety of industrial machines such as towed portable generators. The typical vertically-extending exhaust pipe used in this type of machine is L-shaped so as to have a vertical portion and a horizontal portion meeting at an elbow. An inlet end of the horizontal portion is connected to an upstream component, such as a muffler, of the machine's exhaust system. An exhaust gas outlet is formed from an open upwardly-facing end of the vertical portion. During operation, exhaust gases generated by the engine pass through the exhaust system components and are emitted from the exhaust gas outlet.
The upwardly-facing exhaust gas outlet of the typical vertically-extending exhaust pipe is exposed to the elements and, hence, is prone to invasion by moisture in the form of rainwater, snow, etc. when the engine is not operating. This moisture can degrade the operation of the exhaust system and lead to corrosion and early failure of the exhaust pipe and exhaust system components. In addition, when an engine having a vertically-extending exhaust pipe opening is started after being stored in a wet environment, the water that has accumulated in the exhaust pipe is ejected from the exhaust pipe by the outwardly flowing exhaust gases. This sooty mixture may soil or stain the operator or structures that are close to the exhaust pipe. Mechanisms therefore have been employed to keep rainwater and other moisture out of engine exhaust systems.
The most common mechanism for inhibiting moisture flow into an exhaust pipe is the rain guard or flapper lid. The typical flapper lid is pivotally mounted on the upper end of the exhaust pipe, covers the upper opening of the exhaust pipe when the engine is not operating, and lifts under pressure of exhaust gases when the engine is operating. While such flapper lids are generally effective at keeping rainwater out of exhaust systems, they must be fairly lightweight and be loosely mounted on the upper end of the exhaust pipe in order to be lifted easily by the exhaust gases without creating excessive back pressure or becoming caked with soot. Such lightweight, loosely fitting metal flapper lids tend to rattle and "clank" a great deal during engine operation. Indeed, it has been discovered that the flapper lid is the noisiest component of an otherwise quiet machine such as a gasoline-powered portable generator. Moreover, these structures tend to be rather flimsy and often fail well before the exhaust pipe requires replacement.
Various other solutions to the problem of exhaust pipe moisture flow have been proposed. For example, U.S. Pat. No. 2,468,961 to W. C. Curphy discloses a moisture-deflecting exhaust pipe attachment consisting of a tube bent so as to form a trap that attaches in a spaced relationship to the upper end of a vertically-extending exhaust pipe by a perforated connector ring. In operation, moisture entering the top of the bent tube flows along the tube walls and out of the attachment at the connector ring before reaching the exhaust pipe. Similarly, U.S. Pat. Nos. 2,887,032 and 2,887,033 to P. H. Wachter, Jr., both disclose an attachment that is mounted onto the upper end of a vertically-extending exhaust pipe and that incorporates a trap and associated drain for preventing rain water from flowing into an engine exhaust system. Such separate attachments are needlessly complex, require fitting to the outlet end of the exhaust pipe, increase the effective height of the exhaust pipe, and may come loose if the fit is not correct.
U.S. Pat. No. 4,450,934 to Max L. Davis discloses a complex trap arrangement disposed within a vertically-extending muffler canister. The trap arrangement includes a deflector plate that 1) channels downwardly flowing rainwater away from the muffler's inlet pipe and out through a drain hole and 2) permits upwardly-flowing exhaust gases to spiral 180 degrees around the deflector plate and out of the muffler. While Davis' solution is integrated with an exhaust system component, lacks the additional fittings associated with other proposed solutions and does not significantly increase the height of the exhaust pipe, it is needlessly complex.
Another, less elaborate solution to the problem of draining moisture from a vertically-extending exhaust pipe is to 1) cut a slot into a lower horizontal portion of the L-shaped exhaust pipe to form a drain and to 2) indent the bottom of the pipe upstream of the slot to form a channel. The channel generally directs rainwater toward the drain so that the rainwater will drain from the exhaust pipe before reaching other exhaust system components such as the muffler. Experience has shown, however, that these slots are only partially effective at preventing water from flowing into other exhaust system components. In addition, if the slots are large enough to provide even a generally effective drain, they seriously weaken the exhaust pipe structure to the point that the exhaust pipe corrodes and fails much sooner than it otherwise would.
Thus, none of the solutions heretofore proposed for addressing the problem of draining moisture from a vertically-extending exhaust pipe provide a compact, simple, quiet, structurally sound, and effective mechanism for achieving the desired result. What is needed therefore is a vertically-extending exhaust pipe which includes a drain for diverting moisture from the engine exhaust system and which is simple, effective, quiet, and does not impair the structural integrity of the exhaust pipe.